Reinforced knitted structure comprising metal fibers

ABSTRACT

The invention relates to a single-bed weft-knitted textile structure comprising stainless steel fibre bundles, in which a reinforcing multifilament insert yarn with a titre of less than 180 Tex is incorporated with tuck stitches into the textile structure in a regular pattern. The insert yarn is, for example, a multifilament stainless steel yarn, or a multifilament glass fibre yarn. In addition, the invention relates to the use of such a textile structure for covering moulds and tempering or press rings which are utilized in the process of forming glass plates, or for the covering of transportation means for glass plates during their forming process.

The invention relates to a knitted textile structure comprising metalfibre bundles and into which a reinforcing multifilament insert yarn isincorporated.

Knitted structures comprising metal fibre bundles are described in thePCT patent application WO 97/04152 of the applicant and are beingutilized in various fields of application.

These knitted fabrics are fairly heavy as a result of the high specificgravity of the stainless steel fibres of which they are constructed.This is certainly the case when the knitted fabrics are reinforced withan insert yarn which is of the same type as the knitted yarn. The highown weight of these knitted fabrics themselves can result in a certainsagging down when they are used as a covering for various supports. Thismeans that the knitted fabrics do not always remain in an equally closefitting position to the contact-forming (more or less horizontal)supports. For certain applications, this constitutes a significantdrawback.

Incorporating a conventional, relatively thick insert yam necessarilyresults in a knitted fabric with relatively large stitches. For manyapplications, however, there is a need for a knitted structure withsmall stitches and reinforced with an insert. But this requires highgauges during knitting, which is not possible if a conventional insertyam is incorporated into the knitted structure. Moreover, during theproduction of such a reinforced knitted fabric there is a realpossibility of knitting defects and damage to the knitting machine.

It is an object of the invention to provide a reinforced, relativelylight and thin knitted textile structure that comprises metal fibrebundles and that manages to avoid the drawbacks of the conventionallyreinforced metal knitted fabrics described above.

In particular, the invention provides for a single-bed weft-knittedtextile comprising stainless steel fibre bundles in which a reinforcingmultifilament insert yarn with a titre of less than 180 Tex isincorporated into the textile structure in a regular pattern, e.g. bymeans of tuck stitches.

The metal fibres (e.g., made of a type of steel from the AISI 300 or 400series, Fecralloy®, Aluchrome® or Nicralloy® which are used in thetextile structure according to the invention can be obtained by shavingthe edge of a roll of foil as described in U.S. pat. No. 4,930,199, orby means of the technique of bundled drawing, such as described forexample in U.S. Pat. No. 3,379,000. The metal fibres have an equivalentdiameter which is understood to be between 2 and 100 μm, and bypreference between 2 and 40 μm. The equivalent diameter is defined hereas the diameter surface area as that of the actual fibre in question.

The multifilament insert yam that is incorporated into the knittedtextile structure according to the invention can be a multifilamentmetal or glass yarn consisting of between 30 and 1500 filaments.

Thus, for example, the insert yarn can be Bekinox® VN continuous yarn,which is composed of between 70 and 300 stainless steel filaments havingan equivalent diameter of between 2 and 30 μm. The portion by weight ofthe insert in the textile structure is typically less than 35%.

In another embodiment, a multifilament glass fibre insert yam can beincorporated into the textile structure which, for example, is composedof E- or C-type glass fibres with a diameter of between 7 and 9 μm. Onaverage, such glass yams comprise from 30 to 150 filaments. Thus thereis a multifilament glass fibre yarn consisting, for example, of 2 singleyarns, each containing 22 C-glass filaments that have a diameter of 7 μmand are twisted around one another. The portion by weight of the insertyarn in the textile structure is less than 25%.

The previously mentioned problem of sagging of the textile structure isthus solved by the use of a relatively light insert yarn, which resultsin a knitted fabric that is lighter in weight and which limits theelasticity of the textile structure in the weft direction. This is avery favourable factor for many applications, including the use of thetextile structure as a covering for support structures that are used inthe process of shaping or forming glass plates, such as car windows, aswill be explained below.

Moreover, a multifilament insert yarn is stronger that a conventionalspun insert yarn of the same thickness, so that with a thinner insertyarn a knitted fabric can be obtained which is at least equally strong.

In addition, a thinner insert yarn hinders the stitch formation processto a lesser extent so that with the same gauges a finer knitted fabric(with smaller stitches) can be obtained as compared to the correspondingconventional reinforced product. Moreover, a thinner insert yarn (withtuck stitches) makes it possible to produce reinforced Knitted fabricswith higher gauges than is conventionally possible.

The weft-knitted structure according to the invention is either flat orcircularly knitted and is flexible. The textile structure has a weightwhich is between 600 and 2000 g/m². Its air permeability is more than400 L/dm²/min with a pressure drop of 100 Pa.

EXAMPLE

Weft-knitted textile structure as a covering support for mouldingelements that are in contact with glass plates during the mouldingprocess.

Great numbers of glass fibre fabrics are conventionally used in themanufacture and moulding of car windows, for example for coveringmoulds, tempering and press rings, glass transportation means etc. Thesefabrics are not very wear resistant, however, and result in less opticalquality in the glass sheets thus moulded.

The use of knitted structures containing metal fibres is also known forthis application. In the PCT patent application WO 94/01373 ofapplicant, for example, heterogeneously knitted fabrics are described,whether or not reinforced with an additional insert yarn, that is of thesame type as the knitted yarn. This product deals with double bedknitted fabrics and the insert yarn is not incorporated with tuckstitches.

These conventional heavy knitted fabrics display the drawback thatduring use they sag down somewhat under their own weight. The causes ofthis are that the fibres lose a certain amount of strength at the hightemperatures, and that each time the glass is pressed, the covering issubjected to a slight traction and a few metal fibres remain stuck onthe glass sheet.

For the application under discussion in this example, however, it is ofutmost importance that the knitted coverings always remain tightlyfitted to the under or upper contact-forming support structure in orderthus to avoid dimensional changes, defects in the glass, andobstructions of the production line in the glass forming process.

As a concrete example of a weft-knittted textile structure according tothe invention that can be utilized for the application in view here, acircular knitted structure was made out of stainless steel of the AISItype 316L, reinforced with a multifilament Bekinox® VN continuous yamhaving a titre of 110 Tex, and comprising 90 filaments with an averageequivalent diameter van 14 μm. The weight of this knitted textilestructure is 1685 g/m². Its air permeability is 540 L/min/dm², at apressure drop of 100 Pa. The portion of weight of the textile structurecomprised by the multifilament insert yarn is 32%.

Through the utilization of a thinner insert yarn, the weight of theknitted fabric itself is smaller, so that the knitted fabric will sagless or not at all.

The utilization of a thinner insert yarn makes it possible to produceknitted fabrics with smaller stitches and/or higher gauges, whichresults in better optical properties in the moulded glass sheets.Despite these smaller stitches, the knitted fabric nonetheless remainssufficiently air permeable.

Furthermore, knitted textile structures into which an insert yarn isincorporated have a larger width than textile structures without insertyam, which makes it possible to shape larger glass plates, in particularcar windows or windshields, of very good optical quality.

What is claimed is:
 1. A single-bed weft-knitted textile structurecomprising stainless steel fibre bundles, characterized in that saidtextile structure further comprises a reinforcing multifilament insertyarn with a titre of less than 180 Tex being incorporated into thetextile structure in a regular pattern with tuck stitches.
 2. A textilestructure according to claim 1, characterised in that the textilestructure is flat or circular knitted.
 3. A textile structure accordingto claim 1, in which the weight of the textile structure is between 600and 2000 g/m².
 4. Textile structure according to claim 1, in which theair permeability of the textile structure is more than 400 L/dm²/minwith a pressure drop of 100 Pa.
 5. Textile structure according to claim1, in which the fibre bundles comprise fibres with an equivalentdiameter that is between 2 and 100 μm.
 6. Textile structure according toclaim 1, in which the metal fibre bundles comprise fibres with anequivalent diameter that is between 2 and 40 μm.
 7. Textile structureaccording to claim 1, in which the multifilament yarn is composed onaverage of between 30 and 1500 filaments.
 8. Textile structure accordingto claim 1, in which the insert yarn is a multifilament stainless steelyarn.
 9. Textile structure according to claim 8, characterised in thatthe portion by weight of the insert yarn in the textile structure isless than 35%.
 10. Textile structure according to claim 1, in which theinsert yam is a glass fibre yarn.
 11. Textile structure according toclaim 10, characterised in that the portion by weight of the weft yarnin the textile structure is less than 25%.
 12. The use of a textilestructure according to claim 1 for covering moulds and tempering orpress rings which are utilized in the process of forming glass plates,or for covering transportation means for glass plates during theirforming process.